The goal of this research is to elucidate the influences that control smooth muscle cell (SMC) differentiation and prevent SMC de-differentiation in culture in order to optimize construction and performance of tissue engineered vascular grafts. Initially, we will study the behavior of mature SMCs in our culture systems. However, because of the potential difficulty associated with obtaining and maintaining differentiated SMCs from adult patients, we will also investigate the potential of two types of SMC progenitors (embryonically-derived 10"1"1/2cells and adult marrow-derived mesenchymal cells), which represent potential cell sources for allogeneic or autologous graft creation, to generate functional, differentiated SMCs in our system. We hypothesize that through control of both biochemical and biomechanical stimuli, attempting to recapitulate the environments experienced during embryonic vascular development, induction and/or maintenance of SMC differentiation can be maximized and that this will lead to improved structural integrity and performance of tissue engineered vascular grafts. The goal of each of the specific aims is to attempt to recapitulate certain developmental conditions and to determine the effects of these biochemical and biomechanical stimuli on differentiation of SMC progenitors and/or maintenance of SMC phenotype for vascular tissue engineering. In each of the aims, studies will first be conducted in 2D culture to characterize cellular responses to TGF-b on surfaces that provide defined ligands for cell adhesion. Following this, cells will be cultured in 3D bioactive hydrogel scaffolds designed to present the optimal combination and quantity of biological factors, as determined in the 2D studies, and to confirm the translation of results from 2D to 3D. Finally, cells will be cultured in 3D tubular constructs formed from bioactive, hydrogel scaffolds in a pulsatile flow bioreactor to evaluate the role of mechanical conditioning in SMC differentiation as well as the possible synergistic effects of biochemical and biomechanical stimulation. Adult and embryonic flow conditions will be evaluated. This course of studies will be performed for each cell type.